The lipopolysaccharide bands were visualized by a fast periodic acid silver-staining method of Fomsgaard et al. (1990). For Western immunoblotting, the lipopolysaccharide was transferred to a nitrocellulose membrane via standard techniques. Blots were probed with mouse monoclonal antibodies (mAbs) specific for either lipopolysaccharide inner core region (mAb

5c-7-4), outer core region (mAb 5c-101) or lipid A (mAb 5c-177) (de Kievit & Lam, 1994). Alkaline phosphatase-conjugated goat anti-mouse immunoglobulin G (Jackson Immunoresearch) was used as the secondary antibody and membranes were developed using the standard 5-bromo-4-chloro-3-indolyl phosphate/nitro blue tetrazolium colorimetric detection (de Kievit & Lam, 1994). To prepare exopolysaccharide, cells were streaked on agar plate containing King’s B medium (King et al., 1954) with gentamicin ERK inhibitor and incubated at 30 °C for 3 days. At the end of the incubation period, cells were scraped from the agar surface, suspended in saline, vortexed and subjected

to centrifugation (35 000 g for 30 min). Exopolysaccharide in the cell-free supernatant was precipitated by addition of 2 volumes of isopropyl alcohol, and recovered by centrifugation. The samples were subsequently freeze-dried for storage. The sugar composition of the exopolysaccharide was analyzed with trifluoroacetic acid hydrolysates by a high-performance anion-exchange chromatography (HPAEC) with a Pulsed Amperometric Detection system (Dionex, Sunnyvale, CA) using a CarboPac™ PA-1 column as described previously (Veeranagouda AZD2281 molecular weight et al., 2009). Because colony morphology has been known to influence MRIP ecological adaptation

of bacteria (Chantratita et al., 2007; Choi et al., 2007; Hansen et al., 2007; Yun et al., 2007), transposon mutants of strain KL28 were screened for changes in colony morphology as compared with that of the wild type, which forms a slightly wrinkled colony on LB agar at 30 °C. Transposon mutant C23 exhibited smooth colony morphology under the same growth conditions. Genetic analysis revealed that the transposon insertion was localized to a gene homologous to that encoding a hypothetical protein (PA5001) found in the lipopolysaccharide core-oligosaccharide (OS) assembly gene cluster in Pseudomonas aeruginosa PAO1 (Poon et al., 2008) (Fig. 1). blastp query using the NCBI database showed that the mutated gene product of C23 contains a highly conserved glycosyltransferase_GTB_type superfamily protein domain. Members of this family catalyze the transfer of sugar moieties from activated donor molecules to specific acceptor molecules, forming glycosidic bonds. The deduced amino acid sequence of the mutated gene in C23 shares 76.5% identity with PA5001 and 51.8% identity with a putative glycosyltransferase (GenBank accession number ABP81457.1) in Pseudomonas stutzeri A1501.